Voice Query QoS based on Client-Computed Content Metadata

ABSTRACT

A method includes receiving an automated speech recognition (ASR) request from a user device that includes a speech input captured by the user device and content metadata associated with the speech input. The content metadata is generated by the user device. The method also includes determining a priority score for the ASR request based on the content metadata associated with the speech input and caching the ASR request in a pre-processing backlog of pending ASR requests each having a corresponding priority score. The pending ASR requests in the pre-processing backlog are ranked in order of the priority scores. The method also includes providing, from the pre-processing backlog, one or more of the pending ASR requests to a backend-side ASR module, wherein pending ASR requests associated with higher priority scores are processed before pending ASR requests associated with lower priority scores.

CROSS REFERENCE TO RELATED APPLICATIONS

This U.S. patent application is a continuation of, and claims priorityunder 35 U.S.C. § 120 from, U.S. patent application Ser. No. 17/310,175,filed on Jul. 23, 2021, which is a national phase application of, andclaims priority under 35 U.S.C. § 371 from, international ApplicationPCT/US2019/016882, filed on Feb. 6, 2019. The disclosures of these priorapplications are considered part of the disclosure of this applicationand are hereby incorporated by reference in their entireties.

TECHNICAL FIELD

This disclosure relates to voice query quality of service (QoS) based onclient-computed content metadata.

BACKGROUND

A speech-enabled environment (e.g., home, workplace, school, automobile,etc.) allows a user to speak a query or a command out loud to acomputer-based system that fields and answers the query and/or performsa function based on the command. The speech-enabled environment can beimplemented using a network of connected microphone devices distributedthrough various rooms or areas of the environment. These devices may usehotwords to help discern when a given utterance is directed at thesystem, as opposed to an utterance that is directed to anotherindividual present in the environment. Accordingly, the devices mayoperate in a sleep state or a hibernation state and wake-up only when adetected utterance includes a hotword. The query processing, whichoccurs at a backend server, is expensive and the server may becomeoverloaded with more queries than it can handle at a given time. Forinstance, hotwords present in television programming/commercials duringlarge events can cause the server to become overloaded resulting in anoutage.

SUMMARY

A voice enabled device (e.g., a user device executing a voice assistant)allows a user to speak a query or a command out loud and field andanswer the query and/or perform a function based on the command. Throughthe use of a “hotword” (also referred to as a “keyword”, “attentionword”, “wake-up phrase/word”, “trigger phrase”, or “voice actioninitiation command”), in which by agreement a predetermined term/phrasethat is spoken to invoke attention for the voice enabled device isreserved, the voice enabled device is able to discern between utterancesdirected to the system (i.e., to initiate a wake-up process forprocessing one or more terms following the hotword in the utterance) andutterances directed to an individual in the environment. Typically, thevoice enabled device operates in a sleep state, or a low power state, toconserve battery power and processes input audio data to detect a spokenhotword. For instance, while in the low power state, the voice enableddevice captures input audio via a microphone and uses a hotword detectortrained to detect the presence of the hotword in the input audio. Whenthe hotword is detected in the input audio, the voice enabled deviceinitiates a wake-up process for processing the hotword and/or any otherterms in the input audio following the hotword.

Typically, after a voice enabled device wakes up by detecting thepresence of the hotword in an utterance of speech (e.g., input audio),the voice enabled device sends the hotword and one or more other termsfollowing the hotword over a network to a server-based processing stack(also referred to as a query processing backend) that includes at leastan automated speech recognizer (ASR) configured to process the hotwordand/or any other terms following the hotword. Here, the ASR may treatthe received audio as an ASR request and transcribe the hotword and/orother terms following the hotword into corresponding text. The text maybe provided to an interpretation layer to determine a voice queryspecified by the input audio and provide the query to an appropriatecomponent to perform an action related to the query. Accordingly, when auser of a voice enabled device utters the following speech: “Hey Google,what restaurants are still open right now?”, the voice enabled devicemay wake-up in response to detecting a hotword (“Hey Google”), andprovide the terms following the hotword that correspond to a voice query(“what nearby restaurants are still open right now?”) to theserver-based processing stack for processing. In this example, the ASRof the server-based processing stack would transcribe the voice queryinto corresponding text, the interpretation layer would determine that asearch for hours of operation of nearby restaurants is needed, and asearch engine would obtain a list of search results containing nearbyrestaurants that are currently open. The search results could beprovided back to the voice enabled device for display or audible output.In some scenarios, the server-based processing stack also includes atext-to-speech (TTS) converter configured to convert the list of searchresults into synthesized speech that is provided back to the voiceenabled device for audible output thereon.

The server-based processing stack is configured to process voice queriesreceived from a plurality of voice enabled devices associated with anentire user population. This could include millions of voice enableddevices sending voice queries for processing by the server-basedprocessing stack. Processing voice queries is an expensive task, and insome situations, the server-based processing stack becomes overloadedwith too many voice queries than it can process at a given time. Forinstance, when hotwords, or other terms that sound similar hotwords, arepresent in large television programming events (e.g., a commercialduring the Superbowl), nearby voice enabled devices (e.g., in proximityto a television in a household) may detect the hotword and issue anun-intended voice query to the server-based processing stack, therebyresulting in a very large spike in traffic at the server-basedprocessing stack. While it is conceivable for the server-basedprocessing stack to simply drop voice queries that are not initiated bya real user and/or not time critical, it is difficult to identify suchqueries without starting the expensive processing.

Implementations herein are directed toward a query processing backend(e.g., server-based processing stack) that receives ASR requests fromvoice enabled devices (e.g., user devices). In addition to each ASRrequest including a corresponding speech input captured by the userdevice that includes a voice query for processing, each ASR request alsoincludes content metadata associated with the speech input that isgenerated by the voice enabled device. Based on the content metadataassociated with the speech input, the query processing backend is ableto determine a priority score for each ASR request and cache the ASRrequest in a pre-processing backlog of pending ASR requests each havinga corresponding priority score and ranked in order of the priorityscores. Thereafter, the query processing backend may provide one or morepending ASR requests from the pre-processing backlog to a backend-sideASR module (or other component of the query processing backend) based onprocessing availability of the backend-side ASR module. Here, ratherthan the backend-side ASR module becoming overloaded during trafficspikes by attempting to process each pending ASR requests on afirst-come first-serve basis, the ASR requests are prioritized such thatthe backend-side ASR module processes pending ASR requests associatedwith higher priority scores before processing pending ASR requestsassociated with lower priority scores. As new ASR requests come in, thepending ASR requests in the pre-processing back-log are re-ordered basedon the priority scores. Ideally, those ASR requests associated withun-intended voice queries that are unlikely initiated by real usersand/or not time critical, are assigned lower priority scores. As such,the ASR requests associated with lower priority scores remain in thepre-processing backlog during traffic spikes so that the backend-ASRmodule will first process ASR requests associated higher priorityscores.

In some examples, priority scores below some threshold may simply resultin the corresponding ASR request being dropped. A low priority scoredetermined from the content metadata may also be a strong indicator thatprocessing of the corresponding ASR request will be unsuccessful. Forinstance, content metadata may indicate a quality of the audioassociated with the speech input is very poor, and thus, poor audioquality can provide indication that it will be difficult for thebackend-ASR module to successfully transcribe the audio data intocorresponding text. At the same time, poor audio quality associated withspeech captured by the voice enabled device may also indicate that auser that spoke the hotword (or similar sounding word) is not in closeproximity to the voice enabled device, and thus, likely did not intendto provide a speech input to the voice enabled device. The contentmetadata could also indicate whether or not the speech input was likelyspoken by a user associated with the voice enabled device. For instance,a hotword detector on the voice enabled device may compare the speechinput to an audio profile for that user and determine whether or not thespeech input was more than likely spoken by that user. When the contentmetadata does indicate that the user did likely speak the speech input,the corresponding ASR request may be assigned a higher priority scorethan if a different user spoke the speech input. On the other hand, whenthe content metadata indicates that a different user or broadcast audiofrom an audio broadcast device (e.g., TV, music speaker, or othernon-human source capable of outputting acoustic sounds) initiated thespeech input, the corresponding ASR request may be assigned a lowpriority score. The content metadata can include any type of datacomputed/generated by the voice enabled device and included in the ASRrequest provided to the query processing backend so that the queryprocessing backend can prioritize the importance of the ASR requestwithout incurring any processing (or at least very limited amount ofprocessing) on the ASR request. In view of the foregoing, the contentmetadata associated with the speech input represents a likelihood thatthe corresponding ASR request will be successfully processed by thebackend-side ASR module and/or a likelihood that processing of thecorresponding ASR request will have an impact on the user associatedwith the voice enabled device.

Speech processing in home devices often occurs at the server and at peaktimes which can create a large backlog of requests for speechprocessing. Some of these requests may be genuine requests whereas somemay be the result of broadcast audio (e.g., audio output from non-humansources such as televisions, radios, or synthesized speech). It is anobject of the invention to provide a method to improve the processing ofa large volume of speech recognition requests. By prioritizing therequests it allows the speech recognition module to process the moreimportant or urgent requests which assign a lower priority to otherrequests. This optimizes the use of the speech recognition module attimes when it is overloaded.

One aspect of the disclosure provides a method for providing quality ofservice for voice queries. The method includes receiving, at dataprocessing hardware of a query processing backend, an automated speechrecognition (ASR) request from a user device. The ASR request includes aspeech input captured by the user device and content metadata associatedwith the speech input. The speech input includes a voice query and thecontent metadata is generated by the user device. The method alsoincludes determining, by the data processing hardware, a priority scorefor the ASR request based on the content metadata associated with thespeech input. The method also includes caching, by the data processinghardware, the ASR request in a pre-processing backlog of pending ASRrequests each having a corresponding priority score. The pending ASRrequests in the pre-processing backlog are ranked in order of thepriority scores. The method further includes providing, by the dataprocessing hardware from the pre-processing backlog, one or more of thepending ASR requests to a backend-side ASR module based on processingavailability of the backend-side ASR module. The pending ASR requestsassociated with higher priority scores are processed by the backend-sideASR module before pending ASR requests associated with lower priorityscores.

Implementations of the disclosure may include one or more of thefollowing optional features. In some implementations, the backend-sideASR module is configured to, in response to receiving each pending ASRrequest from the pre-processing backlog of pending ASR requests, processthe pending ASR request to generate an ASR result for a correspondingspeech input associated with the pending ASR request. In some examples,the method further includes, in response to caching one or more new ASRrequests in the pre-processing backlog of pending ASR requests,re-ranking, by the data processing hardware, the pending ASR requests inthe pre-processing backlog in order of the priority scores. Additionallyor alternatively, the method may include rejecting, by the dataprocessing hardware, any pending ASR requests residing in thepre-processing backlog for a period of time that satisfies a timeoutthreshold from being processed by the backend-side ASR module. In someimplementations, the method further includes, in response to receiving anew ASR request having a respective priority score less than a priorityscore threshold, rejecting, by the data processing hardware, the new ASRrequest from being processed by the backend-side ASR module.

The content metadata associated with the speech input may represent alikelihood that the corresponding ASR will be successfully processed bythe backend-side ASR module. In some implementations, the contentmetadata associated with the speech input represents a likelihood thatprocessing of the corresponding ASR request will have an impact on auser associated with the user device. The content metadata associatedwith the speech input and generated by the user device may include atleast one of: a login indicator indicating whether or not a userassociated with the user device is logged in to the user device; aspeaker-identification score for the speech input indicating alikelihood that the speech input matches a speaker profile associatedwith the user device; a broadcasted-speech score for the speech inputindicating a likelihood that the speech input corresponds to broadcastedor synthesized speech output from a non-human source; a hotwordconfidence score indicating a likelihood that one or more termspreceding the voice query in the speech input corresponds to apredefined hotword; an activity indicator indicating whether or not amulti-turn-interaction is in progress between the user device and thequery processing backend; an audio signal score of the speech input; aspatial-localization score indicating a distance and position of a userrelative to the user device; a transcription of the speech inputgenerated by an on-device ASR module residing on the user device; a userdevice behavior signal indicating a current behavior of the user device;or an environmental condition signal indicating current environmentalconditions relative to the user device.

In some implementations, the user device is configured to, in responseto detecting a hotword that precedes the voice query in a spokenutterance: capture the speech input including the voice query; generatethe content metadata associated with the speech input; and transmit thecorresponding ASR request to the data processing hardware. The speechinput may further include the hotword. In some examples, the methodfurther includes transmitting, from the data processing hardware,on-device processing instructions to the user device. The on-deviceprocessing instructions provide one or more criteria for locallyprocessing at least a portion of any new speech inputs captured by theuser device on-device when the user device determines the queryprocessing backend is overloaded. In these example, the user device maybe configured to determine the query processing backend is overloaded byat least one of: obtaining historical data associated with previous ASRrequests communicated by the user device to the data processinghardware; receiving, from the data processing hardware, a schedule ofpast and/or predicted overload conditions at the query processingbackend; or receiving an overload condition status notification from thedata processing hardware on the fly indicating a present overloadcondition at the processing backend. Moreover, the one or more criteriafor locally processing at least the portion of any new speech inputs mayinclude instructing the user device to at least one of: transcribe a newspeech input using a local ASR module residing on the device; interpretthe transcription of the new speech input to determine a voice querycorresponding to the new speech input; determine whether the user devicecan execute an action associated with the voice query corresponding tothe new speech input; or transmit the transcription of the speech inputto the query processing system when the user device is unable to executethe action associated with the voice query. In some implementations, theon-device processing instructions that provide the one or more criteriainclude one or more thresholds that corresponding portions of thecontent metadata must satisfy in order for the user device to transmitthe ASR request to the query processing backend. In some examples, theon-device processing instructions further instruct the user device todrop the ASR request when at least one of the thresholds aredissatisfied.

Another aspect of the disclosure provides a system for providing qualityof service for voice queries. The system includes data processinghardware of a query processing backend and memory hardware incommunication with the data processing hardware. The memory hardwarestores instructions that when executed on the data processing hardwarecause the data processing hardware to perform operations. The operationsinclude receiving an automated speech recognition (ASR) request from auser device. The ASR request includes a speech input captured by theuser device and content metadata associated with the speech input. Thespeech input includes a voice query and the content metadata isgenerated by the user device. The operations also include determining apriority score for the ASR request based on the content metadataassociated with the speech input and caching the ASR request in apre-processing backlog of pending ASR requests each having acorresponding priority score. The pending ASR requests in thepre-processing backlog are ranked in order of the priority scores. Theoperations further include providing, from the pre-processing backlog,one or more of the pending ASR requests to a backend-side ASR modulebased on processing availability of the backend-side ASR module. Thepending ASR requests associated with higher priority scores areprocessed by the backend-side ASR module before pending ASR requestsassociated with lower priority scores.

This aspect may include one or more of the following optional features.In some implementations, the backend-side ASR module is configured to,in response to receiving each pending ASR request from thepre-processing backlog of pending ASR requests, process the pending ASRrequest to generate an ASR result for a corresponding speech inputassociated with the pending ASR request. In some examples, theoperations further include, in response to caching one or more new ASRrequests in the pre-processing backlog of pending ASR requests,re-ranking the pending ASR requests in the pre-processing backlog inorder of the priority scores. Additionally or alternatively, theoperations may further include rejecting any pending ASR requestsresiding in the pre-processing backlog for a period of time thatsatisfies a timeout threshold from being processed by the backend-sideASR module. In some implementations, the operations further include, inresponse to receiving a new ASR request having a respective priorityscore less than a priority score threshold, rejecting the new ASRrequest from being processed by the backend-side ASR module.

The content metadata associated with the speech input may represent alikelihood that the corresponding ASR request will be successfullyprocessed by the backend-side ASR module. In some examples, the contentmetadata associated with the speech input represents a likelihood thatprocessing of the corresponding ASR request will have an impact on auser associated with the user device. The content metadata associatedwith the speech input and generated by the user device may include atleast one of: a login indicator indicating whether or not a userassociated with the user device is logged in to the user device; aspeaker-identification score for the speech input indicating alikelihood that the speech input matches a speaker profile associatedwith the user device; a broadcasted-speech score for the speech inputindicating a likelihood that the speech input corresponds to broadcastedor synthesized speech output from a non-human source; a hotwordconfidence score indicating a likelihood that one or more termspreceding the voice query in the speech input corresponds to apredefined hotword; an activity indicator indicating whether or not amulti-turn-interaction is in progress between the user device and thequery processing backend; an audio signal score of the speech input; aspatial-localization score indicating a distance and position of a userrelative to the user device; a transcription of the speech inputgenerated by an on-device ASR module residing on the user device; a userdevice behavior signal indicating a current behavior of the user device;or an environmental condition signal indicating current environmentalconditions relative to the user device.

In some implementations, the user device is configured to, in responseto detecting a hotword that precedes the voice query in a spokenutterance: capture the speech input including the voice query; generatethe content metadata associated with the speech input; and transmit thecorresponding ASR request to the data processing hardware. The speechinput may further include the hotword. In some examples, the operationsfurther include transmitting on-device processing instructions to theuser device. The on-device processing instructions provide one or morecriteria for locally processing at least a portion of any new speechinputs captured by the user device on-device when the user devicedetermines the query processing backend is overloaded. In theseexamples, the user device may be configured to determine the queryprocessing backend is overloaded by at least one of: obtaininghistorical data associated with previous ASR requests communicated bythe user device to the data processing hardware; receiving, from thedata processing hardware, a schedule of past and/or predicted overloadconditions at the query processing backend; or receiving an overloadcondition status notification from the data processing hardware on thefly indicating a present overload condition at the processing backend.In further examples, the one or more criteria for locally processing atleast the portion of any new speech inputs includes instructing the userdevice to at least one of: transcribe a new speech input using a localASR module residing on the device; interpret the transcription of thenew speech input to determine a voice query corresponding to the newspeech input; determine whether the user device can execute an actionassociated with the voice query corresponding to the new speech input;or transmit the transcription of the speech input to the queryprocessing system when the user device is unable to execute the actionassociated with the voice query. In some implementations, the on-deviceprocessing instructions that provide the one or more criteria includeone or more thresholds that corresponding portions of the contentmetadata must satisfy in order for the user device to transmit the ASRrequest to the query processing backend. In some examples, the on-deviceprocessing instructions further instruct the user device to drop the ASRrequest when at least one of the thresholds are dissatisfied.

The details of one or more implementations of the disclosure are setforth in the accompanying drawings and the description below. Otheraspects, features, and advantages will be apparent from the descriptionand drawings, and from the claims.

DESCRIPTION OF DRAWINGS

FIG. 1 schematically illustrates an example system for prioritizingpending automated speech recognition (ASR) requests received from userdevices.

FIG. 2 schematically illustrates an example user device generatingcontent metadata associated with a speech input captured by the userdevice.

FIGS. 3A-3C schematically illustrate an example voice query quality ofservice (QoS) manager configured to continuously re-rank pending ASRrequests.

FIG. 4 schematically illustrates a QoS manager of FIG. 1 providingon-device processing instructions to a user device.

FIG. 5 is a flowchart of an example arrangement of operations for amethod of processing pending ASR requests at a query processing stackbased on processing availability at the query processing stack.

FIG. 6 is a flowchart of an example arrangement of operations for amethod of executing on-device processing instructions when aserver-based query processing stack is overloaded.

FIG. 7 is a schematic view of an example computing device that may beused to implement the systems and methods described herein.

Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION

Referring to FIG. 1, in some implementations, a system 100 includes userdevices 200, 200 a-n each associated with a user 10, 10 a-n, who maycommunicate, via network 130, with a remote system 140. Some users 10may be associated with more than one user device 200 and/or some userdevices 200 may be associated with more than one user 10 (e.g., familymembers of a household). The remote system 140 may be a distributedsystem (e.g., cloud computing environment) having scalable/elasticresources 142. The resources 142 include computing resources 144 (e.g.,data processing hardware) and/or storage resources 146 (e.g. memoryhardware). In some implementations, the remote system 140 includes avoice query quality of service (QoS) manager 300 and a query processingstack 700, 700 a. The query processing stack 700 a may be referred to asa query processing backend, a server-based or backend-side queryprocessing stack 700 a. The QoS manager 300 is configured to receive anautomatic speech recognition (ASR) request 102 that includes audio data103 and content metadata 110 associated with a speech input 104 from theuser device 200. The QoS manager 300 may then assign a priority score311 to the ASR request 102 based on at least the content metadata 110.Using the priority score 311 assigned to each ASR request 102 receivedand based on processing availability of the query processing stack 700,the QoS manager 300 assigns a corresponding ranking 312 to each ASRrequest 102 and provides the ASR requests 102 to the query processingstack 700 in order of ranking 312 from highest to lowest, i.e., ASRrequests having rankings 312 associated with higher priority scores 311are processed by the query processing stack 700 before ASR requests 102having rankings 312 associated with lower priority scores 311.

The user device 200 includes data processing hardware 204 and memoryhardware 206. The user device 200 may include an audio capture device(e.g., microphone) for capturing and converting the speech input 104from the user 10 into the audio data 103 (e.g., electrical signals). Insome implementations, the data processing hardware 204 is configured toexecute a query processing stack 700, 700 b instead of or in lieu of thequery processing stack 700 a executing on the remote system 140. Forinstance, the query processing stack 700 b may include some of the sameor different components as the query processing stack 700 a executing onthe remote system 140 such as, without limitation, at least one of anon-device ASR module 220 n (FIG. 2), an interpreter module 720, or atext-to-speech (TTS) module 730. In some examples, the user device 200executes an on-device ASR module 220 n (FIG. 2) for generatinglow-fidelity transcriptions quickly and without requiring a networkconnection, whereas the remote system 140 executes a server-based ASRmodule 710 capable of generating high-fidelity transcriptions at theexpense of higher latency compared to the on-device low-fidelitytranscriptions. The user device 200 can be any computing device capableof communicating with the remote system 140 through the network 130. Theuser device 200 includes, but is not limited to, desktop computingdevices and mobile computing devices, such as laptops, smart speakers,smart displays, tablets, smart phones, and wearable computing devices(e.g., headsets and/or watches).

In the example shown, the user 10 may provide the speech input 104 tothe user device 200 by speaking and the user device 200 can capture andconvert the speech input 104 into the audio data 103. The user device200 may then transmit an ASR request 102 that includes the audio data103 and content metadata 110 associated with the speech input 104 to theQoS manager 300 a executing on the remote system 140. Here, the QoSmanager 300 assigns a ranking 312 to the ASR request 102 based on atleast the content metadata 110 and sends the ASR request 102 to thequery processing stack 700 in order of highest ranking 312 to lowestranking 312. The user device 200 may optionally execute the queryprocessing stack 700 b on-device to process the ASR request 102, or someportion of the ASR request 102. For instance, when networkcommunications are down or not available, the user device 200 mayexecute the query processing stack 700 b locally to process the ASRrequest 102. In some examples, the user device 200 may execute the queryprocessing stack 700 b locally to process the ASR request 102 when it isdetermined that the ASR request 102 is time sensitive, for example, anASR request 102 to set a timer for one minute. Implementations hereinfurther include the user device 200 executing the query processing stack700 b locally in scenarios when the QoS manager 300 a executing on theremote system 140 determines/detects that the server-based queryprocessing stack 700 is overloaded and/or presently experiencing a largespike in ASR requests 102 to process.

The content metadata 110 obtained by the QoS manager 300 may include atleast one of a speech recognition category associated with the speechinput 104, an application running on the user device 200 associated withthe user 10, a location of the user 10 at the time the speech input 104was received, a user identifier identifying the user 10, demographicinformation associated with the user 10, whether the user 10 is signedin to the user device 200, whether the user 10 is currently part of amulti-turn interaction with the system 100, spatial-localizationinformation which determines the distance and position of the user 10relative to the user device 200, or ad-likeliness information obtainedby executing an add classifier on the user device 200 that leveragesdata/information from a plurality of sources 220, 220 a-n (FIG. 2).Specifically, and described in greater detail below with reference toFIG. 2, the user device 200 is configured to generate the contentmetadata 110 associated with each speech input 104 and provide theassociated ASR request 102 that includes the content metadata 110 andthe speech input 104 (e.g., audio data 103) to the QoS manager 300 aexecuting on the remote system 140.

The QoS manager 300 includes a ranker 310 and a pre-processing backlog320. The ranker 310 is configured to analyze the content metadata 110contained in the ASR request 102 to determine the likelihood that theASR request 102 is genuine, and assign the ASR request 102 acorresponding ranking 312 based on the likelihood that the ASR request102 is genuine. As used herein, a “genuine” ASR request 102 refers to anASR request 102 including a speech input 104 that was spoken by a realuser 10 and directed to the user device 200 as a voice query forprocessing by the query processing stack 700. In some examples, the QoSmanager 300 determines a corresponding priority score 311 for eachreceived ASR request 102 based on the content metadata 110 contained inthe ASR request 102. Here, the QoS manager 300 may assign the ranking312 to each ASR request 102 based on the corresponding priority score311. Thus, the priority score 311 based on the content metadata 110 foreach received ASR request 102 may indicate the likelihood that the ASRrequest is genuine. For example, the content metadata 110 may indicatethat the ASR request 102 came from a source other than one of the users10, 10 a-n, such as from a non-human source (e.g., television or radio)12 during a television/radio commercial, announcement, or otherprogramming. Accordingly, the ranker 310 determines a low priority score311 for the ASR request 102 since the content metadata 110 indicatesthat the ASR request 102 is likely not genuine, thereby causing theranker 310 to assign a low ranking 312 to the ASR request 102 based on alow likelihood that the ASR request 102 is genuine. In other examples,the content metadata 110 indicates that the ASR request 102 came fromone of the users 10, 10 a-n, thus, the ranker 310 may determine a highpriority score 311 for the ASR request 102 and assign a high ranking 312to the ASR request 102 based on a high likelihood that the ASR request102 is genuine. Additionally or alternatively, the ranker 310 mayanalyze the audio data 103, and/or any other suitable information, inaddition to or instead of the content metadata 110 to determine alikelihood that the ASR request 102 is genuine.

After determining the priority score 311 and assigning the ranking 312for each ASR request 102, the ranker 310 caches the ASR request 102 inthe pre-processing backlog 320 of pending ASR requests 102 each having acorresponding priority score 311 (previously determined by the ranker310). Here, the pending ASR requests 102 in the pre-processing backlog320 are ranked in order of the priority scores 311 such that the queryprocessing stack 700 processes pending ASR requests 102 associated withhigher rankings 312 before processing pending ASR requests 102associated with lower rankings 312.

The ranker 310 continuously, or semi-continuously, receives a list 322of pending ASR requests 102 in the pre-processing backlog 320 andre-ranks the pending ASR requests 102 as new ASR requests 102 arereceived over the network 130 by the QoS manager 300. For example, theranker 310 may determine that a new ASR request 102 has a correspondingpriority score 311 higher than any priority score 311 in the list 322 ofpending ASR requests 102 currently cached in the pre-processing backlog320 while waiting to be processed by the query processing stack 700. Thebacklog 320 may provide the list 322 of pending ASR requests 102 to theranker 310 as feedback and the ranker 310 may assign the new ASR request102 a higher ranking 312 than the rankings 312 in the list 322 ofpending ASR requests 102, such that the new ASR request 102 takesprecedence over the other pending ASR requests 102 in the backlog 320for processing by the query processing stack 700. In someimplementations, the ranker 310 drops at least one of the pending ASRrequests 102 in the list 322. For example, the ranker 310 may determinethat an amount of pending ASR requests 102 in the backlog 320 exceeds apredetermined threshold value. To clear space and/or increase bandwidthin the backlog 320 for new ASR requests 102 with higher rankings 312,the ranker 310 may drop at least one of the pending ASR requests 102associated with a lower ranking 312. Additionally or alternatively, theranker 310 may drop at least one of the pending ASR requests 102 in thelist 322 of pending ASR requests 102 that have timed out, i.e., havebeen pending in the backlog 320 for a time duration exceeding apredetermined threshold value.

Each pending ASR request 102 in the pre-processing backlog 320 iswaiting to be processed by the query processing stack 700 based on therankings 312 assigned to the pending ASR requests 102. For example, thehighest ranked ASR request 102 (e.g., the ASR request 102 associatedwith the highest priority score 311) is processed before the secondhighest ranked ASR request 102 (e.g., the ASR request 102 associatedwith the next highest priority score 311), the second highest ranked ASRrequest 102 is processed before the third highest ranked ASR request102, etc. The backlog 320 continuously, or semi-continuously,communicates the list 322 to the ranker 310 to facilitate re-ranking ofthe pending ASR requests 102.

The query processing stack 700, 700 a on the remote system 140 receiveseach ASR request 102 that has not been dropped or timed out, includingthe audio data 103 and content metadata 110 associated with the speechinput 104, from the QoS manager 300 in descending order of ranking 312.The query processing stack 700 includes at least the ASR module 710, theinterpreter module 720, or the TTS module 730. The ASR module 710 mayperform a variety of operations on the ASR request 102, such as, forexample, processing, noise modeling, acoustic modeling, language model,annotation, etc., to generate a speech recognition result (e.g.,transcription) for the speech input 104. The ASR module 710 sends thisspeech recognition result to the interpreter 720 to determine an intentof the ASR request 102 and generate a response. For example, an ASRrequest 102 requesting the current time would be satisfied by the queryprocessing stack 700 determining and generating a response of thecurrent time in the time zone of the user 10. The TTS module 730 mayconvert this response from text to speech and output the response inaudio form to the user device 200, which is then output as synthesizedspeech to the user 10 via, for example, speakers of the user device 200.Additionally or alternatively, the response may be outputted to the userdevice 200 in text form, which is then transmitted to the user 10 via,for example, a screen of the user device 200. In other implementations,the user device 200 may receive a response in the form of text or otherdata from the query processing stack 700 a and convert the response tospeech using an on-device TTS module.

FIG. 2 shows an example user device 200 capturing a speech input 104,collecting information/data from one or more of the plurality of sources220, 220 a-n, and generating content metadata 110 associated with thespeech input 104 for inclusion in an ASR request 102 sent to the QoSmanager 300. The user device 200 includes a screen 212 and executes agraphical user interface 214 for display on the screen 212. As shown inFIG. 2, the speech input 104 corresponds to a hotword (“Hey Google”) andfollowing voice query directed to the user device 200, e.g., a calendarapplication 220 e executing on the user device 200, to add an event(Skip Fikany's birthday) on a given day (December 8^(th)) to thecalendar application 200 e. In some implementations, the user device 200presents a transcription of the speech input 104 in a voicesearch/command window 216 displayed in the graphical user interface 214.

After the user device 200 receives the speech input 104, the user device200 leverages information/data associated with the speech input 104 fromthe plurality of sources 220 and executes a signal generator 218 (on thedata processing hardware 204) to generate the content metadata 110 thatmay be used to provide context or hints about the speech input 104 foruse by the QoS manager 300 without requiring the QoS manager 300 or thequery processing stack 700 executing on the remote system 140 to startprocessing the ASR request 102. The content metadata 110 associated withthe speech input 104 and generated by the signal generator 218 includesat least one of a login indicator indicating whether or not a user 10associated with the user device 200 is logged in to the user device 200;a speaker-identification score for the speech input 104 indicating alikelihood that the speech input matches a speaker profile associatedwith the user device 200; a broadcasted-speech score for the speechinput 104 indicating a likelihood that the speech input 104 correspondsto broadcasted or synthesized speech output from a non-human source(e.g., a television); a hotword confidence score indicating a likelihoodthat one or more terms detected in the speech input 104 that precede thevoice query corresponds to a hotword; an activity indicator indicatingwhether or not a multi-turn-interaction is in progress between the userdevice 200 and the query processing stack 700 (i.e., the queryprocessing backend); an audio signal quality metric of the speech input104; a spatial-localization score indicating a distance and position ofa user 10 relative to the user device 200; a transcript (e.g.,low-fidelity transcript) of the speech input 104 generated by theon-device ASR module 220 n; a user device behavior signal indicating acurrent behavior of the user device 200; or an environmental conditionsignal indicating current environmental conditions relative to the userdevice 200.. The plurality of sources 220 include, without limitation,at least one of a speaker classifier 220, 220 a, a broadcast audioclassifier 220, 200 b, a hotword detector 220, 220 c, a session activitylog, 220, 220 d, one or more applications 220, 220 e executing on theuser device 200, an audio quality scorer 220, 220 f, one or more sensors220, 220 g of the user device 200, and the on-device ASR 220, 220 n. Aswill become apparent, the signal generator 218 is configured to leveragedata/information from any of the sources 220, as well as any otherrelevant sources, for generating the content metadata 110 associatedwith the speech input 104. Moreover, data/information obtained from twoor more sources 220 more overlap, enabling the signal generator 218 togenerate more robust content metadata 110.

The speaker classifier 220 a may compare audio data 103 (e.g., acousticfeatures related to pronunciation, timing, etc.) of the speech input 104to acoustic features for a speaker profile associated with one or moreusers 10 of the user device 200. For example, the speaker profile may belearned and/or generated during a speaker enrollment process by one ormore users 10 of a household that are authorized to use a user device200, such as a smart speaker. If the audio data 103 of the speech input104 matches the acoustic features of the speaker profile for one or moreusers 10 associated with user device 200, the speaker classifier 220 amay output a high speaker-identification score indicating that thespeech input 104 was likely spoken by a user 10 associated with the userdevice 200. In this instance, the signal generator 218 could use thehigh speaker-identification score to provide content metadata 110indicating a high likelihood that the corresponding ASR request 102 isgenuine. On the other hand, the speaker classifier 220 a may provide alow speaker-identification score when the audio data 103 of the speechinput 104 does not match acoustic features of a speaker profile for auser 10 associated with the user device 200. Accordingly, thespeaker-identification score may correspond to a confidence value orprobability of the audio data 103 matching a known speaker profile.

The broadcast audio classifier 220 b may analyze the audio data 103 ofthe speech input 104 to provide the broadcasted-speech score for thespeech input indicating the likelihood that the speech input 104corresponds to broadcasted or synthesized speech output from a non-humansource 12, such as, for example, a television, a radio, a computer, orany other audio output device capable of outputting broadcasted and/orsynthesized speech. As used herein, broadcasted speech refers to speechspoken by a human (e.g., newscaster, actor, radio personality, etc.) butthat corresponds to audio content emanating/broadcasting from anon-human source 12 during a media event, such as a commercial, radioprogram, television show, and/or movie. Synthesized speech, on the otherhand, refers to non-human speech generated by, for example, atext-to-speech (TTS) system. The broadcast audio classifier 220 b may becapable of detecting watermarks or other features that may be appendedto audio content emanating/broadcasting from a non-human source 12and/or may be self-learning to differentiate between speech output fromreal humans in proximity to the user device 200 and speech output fromnon-human sources 12 that is synthesized speech or being broadcastedduring a media event.

In some examples, the broadcast audio classifier 220 b also analyzes thespeaker-identification score provided by the speaker classifier 220 a asa basis for determining the broadcasted-speech score. For instance, ahigh speaker-identification score output from the speaker classifier isa strong indication that the speech input 104 was not output from anon-human source 12, whereas a low speaker-identification score outputfrom the speaker classifier 220 a opens up the possibility that thespeech input 104 may have emanated from the non-human source 12.

The hotword detector 220 c calculates the hotword confidence score forthe speech input 104 and compares the hotword confidence score to ahotword confidence score threshold. The hotword confidence scorethreshold represents a hotword confidence score that, when detected bythe hotword detector 220 c, triggers the user device 200 to wake-up froma sleep-state to capture the remaining portion of the speech input 104that corresponds to the voice query and generate the ASR request 102 tobe sent to the query processing stack 700. In instances where a user 10speaks a designated hotword “Ok Google” clearly and is near the userdevice 200, the hotword confidence score may be high (e.g., >0.9). Insome instances, a user 10 near the user device 200 may speak a phrasesuch as “Ok poodle” that sounds similar to the designated hotword “OkGoogle”, thereby resulting in a lower confidence score (e.g., 0.7) butstill satisfying the hotword confidence score threshold (e.g., 0.68).Moreover, hotword confidence scores may decrease if the speaker isfarther from the user device 200 or speaks less clearly. Accordingly,providing content metadata 110 that includes the hotword confidencescore of the speech input 104 (i.e., an initial portion of the speechinput 104) may indicate that although the hotword confidence scorethreshold was satisfied to trigger the user device 200 to wake-up, thehotword confidence score may be low enough to indicate that the speakerwas far away and/or spoke some other phrase that sounds similar to thehotword and therefore did not intend to invoke the user device 200.Thus, the hotword confidence score can contribute to content metadata110 indicating whether or not the ASR request is likely genuine.

The session activity log 220 d may provide a log of interactions betweenthe user device 200 and the query processing stack 700. For example, thelog 220 d may include timestamps of recent ASR requests 102 sent to thequery processing stack 700 and corresponding TTS responses returned fromthe query processing stack. The signal generator 218 may access thesession activity log 220 d to determine content metadata 110 indicatingwhether or not a multi-turn interaction is in progress between the userdevice 200 and the query processing stack 700. For example, if the ASRrequest 102 is for a voice query that asks “Should I bring an umbrella”,the session activity log 220 d may show that the user device 200 justprovided a previous voice query asking “What is the temperature going tobe tomorrow morning in Detroit” and received a TTS response from thequery processing stack 700 that stated “The temperature in Detroittomorrow will be 62-degrees at 7 am and will reach 73-degrees by 11 am.”Accordingly, the signal generator 218 may generate content metadata 110for inclusion in the ASR request 102 indicating that the ASR request 102is likely genuine because the user 10 is presently involved in acontinuing discussion with the user device 200. In another example, theuser 10 may have recently submitted an ASR request 102 asking the userdevice 200 to search for local restaurants. If a subsequent ASR request102 is submitted requesting the user device 200 to make a reservation atone of the local restaurants, the session activity log 220 d mayindicate that a multi-turn interaction is in progress between the userdevice 200 and the query processing stack 700. Moreover, the signalgenerator 218 could further determine that a specific application 220 e,such as a digital voice assistant, is currently executing on the userdevice 200 to provide the activity indicator for amulti-turn-interaction in progress between the user device 200 and thequery processing stack is in progress. In some examples, the digitalvoice assistant application 220 e logs session activity in the sessionactivity log 220 d for use by the signal generator 218.

The audio quality scorer 220 f may be configured to determine the audioquality score of the speech input. In some examples, the audio qualityscorer 220 f measures a loudness (e.g., decibels) of the audio data 103associated with the speech input 104. The measured loudness maycorrespond to the portion of the audio data 103 that corresponds to thehotword detected by the hotword detector 220 c, the portion of the audiodata 103 that corresponds to the voice query following the hotword, orthe entire audio data 103 captured by the user device 200. The audioquality score of the speech input 104 may further indicate a level ofbackground noise present in the audio data 103. Thus, the audio qualityscore may simply refer to a confidence score of the audio quality of thespeech input 104, i.e., how well the speech input 104 was captured by amicrophone of the user device 200

The signal generator 218 may determine the content metadata 110including the spatial-localization score for the speech input 104 byleveraging data/information from multiple sources 220 in order to, forexample, indicate a distance and position of a user 10 relative to auser device 200. In some examples, the hotword confidence score from thehotword detector 220 c and/or the audio quality score from the audioquality scorer 220 f may contribute to the spatial-localization score.For instance, a low hotword confidence score and/or a low audio qualityscore may be used to indicate that a source (e.g., user 10) that spokethe speech input 104 is not nearby the user device 200.

Additionally or alternatively, the spatial-localization score may bebased on data/information collected by one or more sensors 220, 200 g ofthe user device 200. The sensors 220 g may include, without limitation,at least one of a light-detecting sensor, an accelerometer, amicrophone, a gyroscope, a magnetometer, a proximity sensor, atouchscreen sensor, a barometer, or a global positioning system (GPS)sensor. For example, if the user device 200 includes a pair of smartheadphones, one or more of the sensors 220 g may be used to determinewhether a user 10 is presently wearing the headphones or whether theheadphones are not being worn, and thus, not in use. Whether or not theuser 10 is wearing the smart headphones may be determined by one of thesensors 220 g, e.g., a proximity sensor, an accelerometer, etc. In thisexample, the signal generator 218 may generate a highspatial-localization score (e.g., binary value of 1) when the user 10 iswearing the smart headphones and a low spatial-localization score (e.g.,binary value of 0) when the user 10 is not wearing the smart headphones.As another example, one of the sensors 220 g may be capable of detectinglight energy in the environment of a user device 200 located in a roomof a house to indicate whether or not the room is dark. For instance, alevel of light energy below a specified threshold may indicate that theuser device 200 is located in a dark room. As such, the signal generator218 may determine a low spatial-localization score when the user device200 is located in a dark room during the evening (e.g., by furtheraccessing the current time of day) to indicate that no users 10 arelikely present in the same room as the user device 200. Conversely, thesignal generator 218 when determining the spatial-localization score mayleverage information from the session activity log 220 d indicating thatthere was a recent ASR request 102 requesting the user device 200 toturn off the lights in the room, and thus, the spatial-localizationscore may instead reflect that there are users 10 in the dark room. Asyet another example, a user device 200 that is part of an infotainmentsystem of a vehicle may use sensors 220 g to determine whether a user 10is in a cabin of the vehicle, whether the vehicle is running, etc. Inthis example, despite the user device 200 capturing a speech input 104,the fact that nobody is in the cabin of the vehicle and the vehicle isnot in operation may indicate that the speech input 104 was directed tosome other user device 200 or was background noise accidently capturedby the infotainment system.

The content metadata 110 including the login indicator may determinewhether a user 10 is logged into the user device 200, e.g., the user 10entered proper credentials to access/unlock the user device 200. Thepresence of a user 10 logged into the user device 200 may increase thelikelihood that the ASR request 102 is genuine. Further, the loginindicator may indicate whether the user 10 is logged into a particularapplication 220 e executing on the user device 200. For example, thesignal generator 218 may generate the login indicator by accessing acalendar application 220 e executing on the user device 200 of thelogged-in user 10 and determine that the logged-in user 10 has a meetingin five minutes. In this example, the login indicator may providecontent metadata 110 that indicates it is important to quickly processthe ASR request 102 for the speech input 104 because the logged-in user10 may need information (e.g., directions, notes, etc.) for the meeting.As another example, the logged-in user 10 may be a homeowner, and thesignal generator 218 may generate the login indicator by accessing thecalendar application 220 e to determine that the logged-in user 10 hasan appointment at a location other than the home of the logged-in user10. If the user device 200 is, for example, a smart speaker located atthe home of the logged-in user 10 and the user device 200 is triggeredupon detecting a spoken hotword at the same time of the appointment inthe calendar application 220 e, the login indicator may provide contentmetadata 110 indicating that there is a high likelihood that thelogged-in user 10 did not provide the speech input 104, therebyrendering the corresponding ASR request 102 as being unlikely genuine.The user 10 may be required to explicitly consent to providing log-ininformation, application use, and location information.

The signal generator 218 may determine the content metadata 110including the user device behavior signal by leveraging data/informationfrom multiple sources 220 in order to, for example, indicate how likelya user 10 is interacting with the user device 200 at the time the speechinput 104 is captured. For instance, information from one or moresensors 220 g may indicate whether the user device is upside down, facedown (e.g., when the user device is a smart phone or tablet), whetherthe user device 200 is in a drawer/purse, etc. In these scenarios, thereis a strong likelihood the user device 200 was accidently triggered,thereby rendering the corresponding ASR request 102 as being unlikelygenuine. Information from sensors 220 g may further include location ofthe user device (e.g., obtained from the GPS sensor 220 g) and/or signalstrength of the user device's 200 network connection. For instance, auser device behavior signal indicating that the user device 200currently has poor signal strength and is at a location notorious forhaving spotty cell coverage (e.g., based on historical knowledge), canbe useful to the QoS manager 300 in prioritizing the corresponding ASRrequest 102 because there is a strong possibility, that even if the ASRrequest 102 is genuine, the user device 200 may not be able to receive acorresponding response (e.g., ASR output and/or TTS response) processedby the query processing stack. In this situation, when the queryprocessing stack 700 is experiencing high traffic spikes, it may bebeneficial to process other pending ASR requests 102 first that willproduce corresponding responses having a stronger likelihood of beingsuccessfully returned back to their respective user devices 200.

The signal generator 218 may determine the content metadata 110including the environmental condition signal by leveragingdata/information from multiple sources 220 in order to, for example,assess and analyze conditions surrounding the user device 200.Specifically, the environmental condition signal may leverage one ormore of the sensors 220 g to determine environmental conditionssurrounding the user device 200. For example, the environmentalcondition signal may indicate that there are several user devices 200 inproximity of the user device 200, conditions of the network the userdevice 200 is connected to (e.g., the network is overloaded), GPScoordinates of the user device 200, whether the user device 200 isoutside, presently moving, approaching an area of poor cellular or datareception, etc.

As set forth in the remarks above, a user device 200 may have theability to execute an on-device ASR module 220 n (e.g., the local queryprocessing stack 700 b) for generating low-fidelity transcriptionsquickly and without requiring a network connection. Advantageously, thecontent metadata 110 generated by the signal generator 218 may include alow-fidelity transcription of the speech input 104 generated by theon-device ASR module 220 n to provide potentially relevant informationor details about the ASR request 102 to the QoS manager 300. Here, thelow-fidelity transcription may reveal that the ASR request 102 includesa time-sensitive voice query (e.g., a command to set a timer for oneminute), thereby informing the QoS manager 300 to assign a high priorityscore 311 to the ASR request 102 so that the ASR request 102 isprocessed immediately. In this same scenario, if the query processingstack 700 a is overloaded and at full processing capacity at the timethe ASR request 102 is cached in the backlog 320, the query processingstack 700 a may be unable to immediately process the ASR request 102(e.g., send instructions to set the timer for one minute) and may simplydrop the ASR request 102 and optionally inform the user 10 that therequest cannot be completed at the moment. This would be preferable tothe user 10 since setting the timer for a short duration is of littleuse after time lapses since providing the ASR request 102. Yet, if thecommand were to set the timer for a longer duration, such as 10 minutes,it may be permissible to allow the ASR request 102 to remain pending andcached in the pre-processing backlog 320 until the query processingstack 700 a is able to process the ASR request 102, whereby theinstructions for setting the timer could compensate for the latencycaused by the increase in traffic while the ASR request 102 was pendingin the pre-processing backlog 320.

In the example shown, after the signal generator 218 compiles andgenerates the content metadata 110 associated with the speech input 104,the user device 200 imbeds the content metadata 110 for inclusion in theASR request 102 together with the corresponding speech input 104 andaudio data 103. The user device 200 then sends the ASR request 102 tothe QoS manager 300.

FIGS. 3A-3C provide schematic views of the voice query QoS manager 300assigning rankings 312 to ASR requests 102 received from user devices200 and providing the ASR requests 102 to the query processing stack 700in order of ranking 312 from highest to lowest based on processingavailability of the query processing stack 700. The query processingstack 700 may include, without limitation, at least one of the ASRmodule 710 (FIG. 1), the interpreter module 720 (FIG. 1), or the TTSmodule 730 (FIG. 1). In the example shown, the query processing stack700 may be currently experiencing a large traffic spike of ASR requests102 that cause the query processing stack 700 to be overloaded. Forexample, a television commercial airing during a large media event(e.g., the Superbowl) may include a spoken hotword that, when outputfrom televisions (e.g., non-human source 12) in user households, causesspeech-enabled user devices 200 in those households to trigger andgenerate false ASR requests 102 that include audio data 103 capturedafter detection of the hotword output from the televisions.

Referring to FIG. 3A, the pre-processing backlog 320 includes pendingASR requests A 102 a, B 102 b, C 102 c waiting to be processed by thequery processing stack 700 when the ranker 310 of the voice query QoSmanager 300 receives a new ASR request D 102 d from a user device 200.The ranker 310 may determine a corresponding priority score 311 for thenew ASR request D 102 d based on the content metadata 110 associatedwith the new ASR request D 102 d. At the time the new ASR request D 102d is received, the pending ASR requests 102 a, 102 b, 102 c in thepre-processing backlog 320 are ranked in order of their priority scores311 such that ASR request A 102 a is associated with a highest ranking312, ASR request C 102 b is associated with the next highest ranking312, and ASR request B 102 b is associated with a lowest ranking 312.Thus, while ASR request C 102 c may have been received at the QoSmanager 300 from a corresponding user device 200 after the QoS manager300 received the ASR request B 102 b, the ranker 310 assigns a rank 312to the ASR request C 102 c that is higher than a rank 312 assigned tothe ASR request B 102 b. The pre-processing backlog 320 can includethousands to millions of pending ASR requests 102 ranked in order ofpriority scores 311 waiting to be processed by the query processingstack 700. With continued reference to FIG. 3A, the pre-processingbacklog 320 provides a list 322 of the pending ASR requests A 102 a, C102 c, B 102 b to the ranker 310 and the ranker 310 re-ranks the pendingASR requests A 102 a, C 102 c, B 102 b together with the new ASR requestD 102 d based on the priority scores.

In some implementations, the ranker 310 rejects any pending ASR requests102 that reside in the pre-processing backlog 320 for a period of timethat satisfies a timeout threshold from being processed by queryprocessing stack 700 (e.g., the backend-side ASR module 710). FIG. 3Bshows the ranker 310 rejecting the pending ASR request B 102 b frombeing processed by the query processing stack 700 since the pending ASRrequest B 102 b satisfies the timeout threshold. For instance, thepending ASR request B 102 b may have included such a low priority score311 that resulted in the ASR request B 102 b staying at the bottom ofthe list 322 so that the ASR request B 102 b never got processed even asnew ASR requests 102 were received later in time. Accordingly, the ASRrequest B 102 b is dropped from the pre-processing backlog 320. FIG. 3Bfurther shows the ranker 310 determining that the new ASR request D 102d includes a priority score 311 that is higher than the priority score311 of the pending ASR request C 102 c and lower than the priority scoreof the pending ASR request A 102 a. As such, the ranker 310 provides are-ranked list 322 of pending ASR requests A 102 a, D 102 d, C 102 c tothe pre-processing backlog 320 such that ASR request A 102 a is stillassociated with a highest ranking 312, ASR request D 102 d is nowassociated with the next highest ranking 312, and ASR request C 102 c isnow associated with a lowest ranking 312. Thus, the new ASR request D102 d ranked higher than the ASR request C 102 c in the list 322 ofpending ASR requests 102 results in the new ASR request D 102 d takingprecedence over the ASR request C 102 c in the backlog 320 forprocessing by the query processing stack 700. The ASR request A 102 a,however, takes precedence over the new ASR request D 102 d forprocessing by the query processing stack 700.

Referring to FIG. 3C, the query processing stack 700 is available toprocess a next pending ASR request 102 cached in the pre-processingbacklog 320. Since, the ASR request A 102 a is associated with thehighest ranking 312 in the list 322 of pending ASR requests 102 waitingto be processed in the pre-processing back log 320, the pre-processingbacklog 320 provides the ASR request A 102 a to the query processingstack 700 for processing. Accordingly, the ASR request A 102 a isremoved from the backlog 320 and the list 322 of pending ASR requests102.

At the same time the ASR request A 102 a is provided to the queryprocessing stack 700 for processing, the ranker 310 of the voice queryQoS manager 300 receives a new ASR request E 102 e from a correspondinguser device 200 and receives, as feedback, the list 322 of the pendingASR requests D 102 d, C 102 c from the pre-processing backlog 320. Here,the ranker 310 may determine a corresponding priority score 311 for thenew ASR request E 102 e based on the content metadata 110 associatedwith the new ASR request E 102 e, and then re-rank the pending ASRrequests D 102 d, C 102 c together with the new ASR request E 102 ebased on the priority scores. The continuous re-ranking of pending ASRrequests 102 in pre-processing backlog 320 as new ASR requests 102 arereceived is an iterative process and is dependent upon processingavailability of the query processing stack 700.

FIG. 4 shows a schematic view 400 of the QoS manager 300 communicatingon-device processing instructions 420 to a user device 200 that allowthe user device 200 to decide whether or not to send ASR requests 102 tothe query processing stack 700 (e.g., query processing backend) forprocessing when a high load condition is present at the query processingstack. The high load condition may indicate the query processing stack700 a is overloaded due to a large traffic spike in the number of ASRrequests 102 sent to the query processing stack 700 for processing. TheQoS manager 300 may provide the on-device processing instructions 420 toall, or selected sub-sets, of a population of voice enabled user devices200 that the query processing stack 700 a is responsible for processing.User devices 200 associated with one device type (e.g., smart speaker)may receive different ASR request instructions 420 than user devices 200associated with another device type (e.g., smart phone). The on-deviceprocessing instructions 420 may provide one or more criteria for locallyprocessing (e.g., at the on-device query processing stack 700 b) atleast a portion of any new speech inputs 104 captured by the user device200 on-device when the user device 200 determines the query processingstack 700 a is overloaded.

The on-device processing instructions 420 may provide criteria forsending ASR requests 102 to the query processing stack 700 a when queryprocessing stack 700 a is overloaded based on the content metadata 110associated with the ASR requests 102.

In some implementations, the on-device processing instructions 420provide one or more thresholds that corresponding portions of thecontent metadata 110 must satisfy in order for the user device 200 totransmit the ASR request 102 to the query processing stack 700 a duringthe high load condition. For instance, the on-device processinginstructions 420 may provide a hotword confidence score threshold that ahotword confidence score must satisfy and/or an audio quality scorethreshold that an audio quality score of a speech input 104 mustsatisfy. While the user devices 200 normally apply default thresholds,the thresholds provided in the on-device processing instructions 420 maybe more conservative so that only ASR requests 102 with a highconfidence of being genuine (or having a high impact on the user) aresent to the query processing stack 700 a for processing. In an example,the user device 200 may normally send ASR requests 102 associated withhotword confidence scores greater than 0.68 to the query processingstack 700 a for processing. However, when the query processing stack 700a is overloaded, the on-device processing instructions 420 may indicatethat ASR requests 102 must be associated with hotword confidence scoresof at least 0.8 in order to be sent to the query processing stack 700 afor processing. The on-device processing instructions 420 may furtherinstruct the user device 200 to drop the ASR request 102 when at leastone of the thresholds are dissatisfied. The QoS manager 300 may send theon-device processing instructions 420 on the fly whenever the high loadcondition is present, or the QoS manager 300 may send the on-deviceprocessing instructions 420 to the user devices 200 at any time so thatthe user devices 200 can apply/execute the on-device processinginstructions 420 when high load conditions occur at later times. Audioquality thresholds can be similarly provided for use by the user devices200 in filtering out ASR requests 102 having audio quality that does notmeet thresholds defined by the instructions 420 when the queryprocessing stack 700 a is overloaded.

In the example shown, the user device 200 captures a speech input 104and generates content metadata 110 associated with the speech input 104.For instance, the user device 200 executes a signal generator 218configured to generate the content metadata 110 based oninformation/data obtained from one or more of the sources 220. Thecontent metadata 110 generated by the user devices 200 is describedabove with reference with FIG. 2. Before sending (or locally processing)a corresponding ASR request 102 that includes the speech input 104 andassociated content metadata 110, the user device 200 may determinewhether a high load condition exists at the query processing stack 700a. In some examples, the user device 200 receives a notification 410(e.g., an overload condition status notification) from the QoS manager300 on the fly indicating the presence of the overload condition at thequery processing stack 700 a. Additionally or alternatively, the userdevice 200 may receive notifications 410 that include a schedule of pastand/or predicted overload conditions at the query processing stack 700a. The user device 200 may store this schedule on the memory hardware206.

In other examples, the user device 200 determines the overload conditionis present at the query processing stack 700 a by obtaining historicaldata 250 (e.g., ASR request history) associated with previous ASRrequests 102 communicated by the user device 200 to the query processingstack 700 a. The historical data 250 may be stored on the memoryhardware 206 of the user device 200 (or stored remotely). The historicaldata 250 may indicate specific dates, days, times, etc. where the userdevice 200 and/or other user devices 200 have experienced scenarios whenthe query processing stack 700 a was overloaded. For example, everyweekday night at approximately 7:36 pm during the last 2-weeks the userdevice 200 has experienced an overload condition at the query processingstack. In this example, a television commercial during the show Jeopardymay include a phrase (“Hey poodle”) spoken by an actor with an accentthat sounds substantially similar to a designated hotword (“Hey Google”)resulting in false triggering of voice enabled devices in a multitude ofhouseholds.

Additionally, the on-device processing instructions 420 may provide oneor more criteria for locally processing at least a portion of any newspeech inputs 104 captured by the user device 200 on-device when theuser device 200 determines the query processing stack 700 a isoverloaded. For instance, the one or more criteria for locallyprocessing at least the portion of any new speech inputs 104 may includeinstructing the user device 200 to at least one of: transcribe a newspeech input 104 using the local ASR module 200 n (e.g., when available)residing on the user device 200; interpret the transcription of the newspeech input 104 to determine a voice query corresponding to the newspeech input 104; determine whether the user device 200 can execute anaction associated with the voice query corresponding to the new speechinput 104; or transmit the transcription of the speech input 104 to thequery processing stack 700 a when the user device 200 is unable toexecute the action associated with the voice query. In someimplementations, the one or more criteria provided by the on-deviceprocessing instructions 420 delegate some portions of the ASR request102 for local processing by the user device 200 while the queryprocessing stack 700 a processes other portions. For instance, the userdevice 200 may include a client-side TTS module so that the queryprocessing stack 700 a can provide an ASR response to the user device200 in text and the user device 200 may use the client-side TTS moduleto generate corresponding synthesized speech. This scenarios wouldalleviate the server-side query processing stack 700 a from having togenerate a TTS response during the overload condition.

FIG. 5 is a flowchart of an example arrangement of operations for amethod 500 of processing pending ASR requests 102 at a query processingstack 700 a (e.g., a backend-side ASR module 710 a at the queryprocessing stack 700 a) based on processing availability at the queryprocessing stack 700 a. At operation 502, the method 500 includesreceiving, at data processing hardware 144 of the query processing stack700 a (e.g. query processing backend), an ASR request 102 from a userdevice 200. The ASR request 102 includes a speech input 104 captured bythe user device 200 that includes a voice query and content metadata 110associated with the speech input 104. The content metadata 110 isgenerated by the user device 200, as described above with reference toFIG. 2. At operation 504, the method 500 includes determining, by thedata processing hardware 144, a priority score 311 for the ASR request102 based on the content metadata 110 associated with the speech input.

At operation 506, the method 500 includes caching, by the dataprocessing hardware 144, the ASR request 102 in a pre-processing backlog320 of pending ASR requests 102 each having a corresponding priorityscore 311. The pending ASR requests 102 in the pre-processing backlog320 are ranked in order of the priority scores 311, as described abovewith reference to FIGS. 3A-3C. The pre-processing backlog 320 may resideon the storage resources (e.g., memory hardware) 146 of the remotesystem 140. At operation 508, the method 500 includes providing, by thedata processing hardware 144 from the pre-processing backlog 320, one ormore of the pending ASR requests 102 to the backend-side ASR module 710(or other module at the query processing stack 700 a) based onprocessing availability of the backend-side ASR module 710. As describedabove with reference to FIGS. 3A-3C, the pending ASR requests 102 in thebacklog 320 that are associated with higher priority scores 311 areprocessed by the backend-side ASR module 710 before the pending ASRrequests 102 associated with lower priority scores 311.

FIG. 6 is a flowchart of an example arrangement of operations for amethod 600 of executing on-device processing instructions when aserver-based query processing stack 700 a is overloaded (e.g., anoverload condition is present at the stack 700 a). The method 600 mayexecute on the data processing hardware 204 of the user device 200. Atoperation 602, the method 600 includes generating an ASR request 102 atthe user device 200. Here, the ASR request 102 includes a speech input104 captured by the user device 200 that includes a voice query, as wellas content metadata 110 generated by the user device 200 and associatedwith the speech input 104. Generating content metadata 110 associatedwith speech inputs 104 is described above with reference to FIG. 2. Atoperation 604, the method includes receiving, at the user device 200,on-device processing instructions 420 from the server-side queryprocessing stack 700 a. For instance, FIG. 4 shows the user device 200receiving the on-device processing instructions 420. The on-deviceprocessing instructions 420 may provide criteria for sending ASRrequests 102 to the query processing stack 700 a when query processingstack 700 a is overloaded based on the content metadata 110 associatedwith the ASR requests 102. In some implementations, the on-deviceprocessing instructions 420 provide one or more thresholds thatcorresponding portions of the content metadata 110 must satisfy in orderfor the user device 200 to transmit the ASR request 102 to the queryprocessing stack 700 a during the overload condition.

At operation 606, the method 600 also includes determining, by the userdevice 200, whether the server-side query processing stack 700 a isoverloaded. As described above in greater detail with reference to FIG.4, the user device 200 may determine the overload condition based on atleast one of historical data 250 (e.g., prediction-based) associatedwith previous ASR requests communicated by the user device 200 (and/orother user devices) to the query processing stack 700 a or uponreceiving a notification 410 from the query processing stack 700 a. Thenotification 410 a may include a schedule of past and/or predictedoverload conditions at the query processing stack 700 a and/or anoverload condition status notification sent by the query processingstack 700 a on the fly to indicate a present overload condition. Atoperation 608, when the user device 200 determines the query processingstack 700 a is overloaded, the method 600 includes executing, by theuser device 200, the on-device processing instructions 420. Executingthe on-device processing instructions 420 by the user device 200 isdescribed above with reference to FIG. 4.

A software application (i.e., a software resource) may refer to computersoftware that causes a computing device to perform a task. In someexamples, a software application may be referred to as an “application,”an “app,” or a “program.” Example applications include, but are notlimited to, system diagnostic applications, system managementapplications, system maintenance applications, word processingapplications, spreadsheet applications, messaging applications, mediastreaming applications, social networking applications, and gamingapplications.

The non-transitory memory may be physical devices used to store programs(e.g., sequences of instructions) or data (e.g., program stateinformation) on a temporary or permanent basis for use by a computingdevice. The non-transitory memory may be volatile and/or non-volatileaddressable semiconductor memory. Examples of non-volatile memoryinclude, but are not limited to, flash memory and read-only memory(ROM)/programmable read-only memory (PROM)/erasable programmableread-only memory (EPROM)/electronically erasable programmable read-onlymemory (EEPROM) (e.g., typically used for firmware, such as bootprograms). Examples of volatile memory include, but are not limited to,random access memory (RAM), dynamic random access memory (DRAM), staticrandom access memory (SRAM), phase change memory (PCM) as well as disksor tapes.

FIG. 7 is schematic view of an example computing device 700 that may beused to implement the systems and methods described in this document.The computing device 700 is intended to represent various forms ofdigital computers, such as laptops, desktops, workstations, personaldigital assistants, servers, blade servers, mainframes, and otherappropriate computers. The components shown here, their connections andrelationships, and their functions, are meant to be exemplary only, andare not meant to limit implementations of the inventions describedand/or claimed in this document.

The computing device 700 includes a processor 711 (e.g., data processinghardware 144), memory 721 (e.g., memory hardware 146), a storage device731, a high-speed interface/controller 740 connecting to the memory 721and high-speed expansion ports 750, and a low speed interface/controller760 connecting to a low speed bus 770 and a storage device 731. Each ofthe components 711, 721, 731, 740, 750, and 760, are interconnectedusing various busses, and may be mounted on a common motherboard or inother manners as appropriate. The processor 711 can process instructionsfor execution within the computing device 700, including instructionsstored in the memory 721 or on the storage device 731 to displaygraphical information for a graphical user interface (GUI) on anexternal input/output device, such as display 780 coupled to high speedinterface 740. In other implementations, multiple processors and/ormultiple buses may be used, as appropriate, along with multiple memoriesand types of memory. Also, multiple computing devices 700 may beconnected, with each device providing portions of the necessaryoperations (e.g., as a server bank, a group of blade servers, or amulti-processor system).

The memory 721 stores information non-transitorily within the computingdevice 700. The memory 721 may be a computer-readable medium, a volatilememory unit(s), or non-volatile memory unit(s). The non-transitorymemory 721 may be physical devices used to store programs (e.g.,sequences of instructions) or data (e.g., program state information) ona temporary or permanent basis for use by the computing device 700.Examples of non-volatile memory include, but are not limited to, flashmemory and read-only memory (ROM)/programmable read-only memory(PROM)/erasable programmable read-only memory (EPROM)/electronicallyerasable programmable read-only memory (EEPROM) (e.g., typically usedfor firmware, such as boot programs). Examples of volatile memoryinclude, but are not limited to, random access memory (RAM), dynamicrandom access memory (DRAM), static random access memory (SRAM), phasechange memory (PCM) as well as disks or tapes.

The storage device 731 is capable of providing mass storage for thecomputing device 700. In some implementations, the storage device 731 isa computer-readable medium. In various different implementations, thestorage device 731 may be a floppy disk device, a hard disk device, anoptical disk device, or a tape device, a flash memory or other similarsolid state memory device, or an array of devices, including devices ina storage area network or other configurations. In additionalimplementations, a computer program product is tangibly embodied in aninformation carrier. The computer program product contains instructionsthat, when executed, perform one or more methods, such as thosedescribed above. The information carrier is a computer- ormachine-readable medium, such as the memory 721, the storage device 731,or memory on processor 711.

The high speed controller 740 manages bandwidth-intensive operations forthe computing device 700, while the low speed controller 760 manageslower bandwidth-intensive operations. Such allocation of duties isexemplary only. In some implementations, the high-speed controller 740is coupled to the memory 721, the display 780 (e.g., through a graphicsprocessor or accelerator), and to the high-speed expansion ports 750,which may accept various expansion cards (not shown). In someimplementations, the low-speed controller 760 is coupled to the storagedevice 731 and a low-speed expansion port 790. The low-speed expansionport 790, which may include various communication ports (e.g., USB,Bluetooth, Ethernet, wireless Ethernet), may be coupled to one or moreinput/output devices, such as a keyboard, a pointing device, a scanner,or a networking device such as a switch or router, e.g., through anetwork adapter.

The computing device 700 may be implemented in a number of differentforms, as shown in the figure. For example, it may be implemented as astandard server 700 a or multiple times in a group of such servers 701,as a laptop computer 703, or as part of a rack server system 705.

Various implementations of the systems and techniques described hereincan be realized in digital electronic and/or optical circuitry,integrated circuitry, specially designed ASICs (application specificintegrated circuits), computer hardware, firmware, software, and/orcombinations thereof. These various implementations can includeimplementation in one or more computer programs that are executableand/or interpretable on a programmable system including at least oneprogrammable processor, which may be special or general purpose, coupledto receive data and instructions from, and to transmit data andinstructions to, a storage system, at least one input device, and atleast one output device.

These computer programs (also known as programs, software, softwareapplications or code) include machine instructions for a programmableprocessor, and can be implemented in a high-level procedural and/orobject-oriented programming language, and/or in assembly/machinelanguage. As used herein, the terms “machine-readable medium” and“computer-readable medium” refer to any computer program product,non-transitory computer readable medium, apparatus and/or device (e.g.,magnetic discs, optical disks, memory, Programmable Logic Devices(PLDs)) used to provide machine instructions and/or data to aprogrammable processor, including a machine-readable medium thatreceives machine instructions as a machine-readable signal. The term“machine-readable signal” refers to any signal used to provide machineinstructions and/or data to a programmable processor.

The processes and logic flows described in this specification can beperformed by one or more programmable processors, also referred to asdata processing hardware, executing one or more computer programs toperform functions by operating on input data and generating output. Theprocesses and logic flows can also be performed by special purpose logiccircuitry, e.g., an FPGA (field programmable gate array) or an ASIC(application specific integrated circuit). Processors suitable for theexecution of a computer program include, by way of example, both generaland special purpose microprocessors, and any one or more processors ofany kind of digital computer. Generally, a processor will receiveinstructions and data from a read only memory or a random access memoryor both. The essential elements of a computer are a processor forperforming instructions and one or more memory devices for storinginstructions and data. Generally, a computer will also include, or beoperatively coupled to receive data from or transfer data to, or both,one or more mass storage devices for storing data, e.g., magnetic,magneto optical disks, or optical disks. However, a computer need nothave such devices. Computer readable media suitable for storing computerprogram instructions and data include all forms of non-volatile memory,media and memory devices, including by way of example semiconductormemory devices, e.g., EPROM, EEPROM, and flash memory devices; magneticdisks, e.g., internal hard disks or removable disks; magneto opticaldisks; and CD ROM and DVD-ROM disks. The processor and the memory can besupplemented by, or incorporated in, special purpose logic circuitry.

To provide for interaction with a user, one or more aspects of thedisclosure can be implemented on a computer having a display device,e.g., a CRT (cathode ray tube), LCD (liquid crystal display) monitor, ortouch screen for displaying information to the user and optionally akeyboard and a pointing device, e.g., a mouse or a trackball, by whichthe user can provide input to the computer. Other kinds of devices canbe used to provide interaction with a user as well; for example,feedback provided to the user can be any form of sensory feedback, e.g.,visual feedback, auditory feedback, or tactile feedback; and input fromthe user can be received in any form, including acoustic, speech, ortactile input. In addition, a computer can interact with a user bysending documents to and receiving documents from a device that is usedby the user; for example, by sending web pages to a web browser on auser's client device in response to requests received from the webbrowser.

A number of implementations have been described. Nevertheless, it willbe understood that various modifications may be made without departingfrom the spirit and scope of the disclosure. Accordingly, otherimplementations are within the scope of the following claims.

What is claimed is:
 1. A computer-implemented method that when executedon data processing hardware of a user device causes the user device toperform operations comprising: generating an automated speechrecognition (ASR) request, the ASR request comprising: a speech inputcaptured by the user device that includes a voice query; and contentmetadata associated with the speech input, the content metadatagenerated by the user device; receiving on-device processinginstructions from a server-side query processing stack; determiningwhether the server-side query processing stack is overloaded; and whenthe server-side query processing stack is overloaded, executing theon-device processing instructions to identify one or more criteria forlocally processing at least a portion of speech input on-device.
 2. Thecomputer-implemented method of claim 1, wherein the content metadataassociated with the speech input represents a likelihood that thecorresponding ASR request will be successfully processed by theserver-side query processing stack.
 3. The computer-implemented methodof claim 1, wherein the content metadata associated with the speechinput represents a likelihood that processing of the corresponding ASRrequest will have an impact on a user associated with the user device.4. The computer-implemented method of claim 1, wherein the contentmetadata associated with the speech input and generated by the userdevice comprises at least one of: a login indicator indicating whetheror not a user associated with the user device is logged in to the userdevice; a speaker-identification score for the speech input indicating alikelihood that the speech input matches a speaker profile associatedwith the user device; or a broadcasted-speech score for the speech inputindicating a likelihood that the speech input corresponds to broadcastedor synthesized speech output from a non-human source.
 5. Thecomputer-implemented method of claim 1, wherein the content metadataassociated with the speech input and generated by the user devicecomprises at least one of: a hotword confidence score indicating alikelihood that one or more terms preceding the voice query in thespeech input corresponds to a predefined hotword; an activity indicatorindicating whether or not a multi-turn-interaction is in progressbetween the user device and the query processing backend; an audiosignal score of the speech input; or a spatial-localization scoreindicating a distance and position of a user relative to the userdevice.
 6. The computer-implemented method of claim 1, wherein thecontent metadata associated with the speech input and generated by theuser device comprises at least one of: a transcription of the speechinput generated by an on-device ASR module residing on the user device;a user device behavior signal indicating a current behavior of the userdevice; or an environmental condition signal indicating currentenvironmental conditions relative to the user device.
 7. Thecomputer-implemented method of claim 1, wherein determining whether theserver-side query processing stack is overloaded is based on at leastone of: historical data associated with previous ASR requestscommunicated by the user device to the server-side query processingstack; a schedule of past and/or predicted overload conditions at theserver-side query processing stack; or receiving an overload conditionstatus notification from the server-side query processing stack on thefly indicating a present overload condition at the server-side queryprocessing stack.
 8. The computer-implemented method of claim 1, whereinexecuting the on-device processing instructions further comprises:transcribing, by the data processing hardware, the speech input using alocal ASR module residing on the user device; interpreting thetranscription of the speech input to determine a voice querycorresponding to the speech input; determining whether the user devicecan execute an action associated with the voice query corresponding tothe speech input; and executing the action associated with the voicequery when the user device is able to execute the action.
 9. Thecomputer-implemented method of claim 1, wherein executing the on-deviceprocessing instructions to identify the one or more criteria comprisesexecuting the on-device processing instructions to identify one or morethresholds that corresponding portions of the content metadata mustsatisfy in order for the user device to transmit the ASR request to theserver-side query processing stack.
 10. The computer-implemented methodof claim 9, wherein the operations further comprise dropping ASR requestwhen at least one of the thresholds are dissatisfied.
 11. A systemcomprising: data processing hardware of a user device; and memoryhardware in communication with the data processing hardware and storinginstructions that when executed on the data processing hardware causethe data processing hardware to perform operations comprising:generating an automated speech recognition (ASR) request, the ASRrequest comprising: a speech input captured by the user device thatincludes a voice query; and content metadata associated with the speechinput, the content metadata generated by the user device; receivingon-device processing instructions from a server-side query processingstack; determining whether the server-side query processing stack isoverloaded; and when the server-side query processing stack isoverloaded, executing the on-device processing instructions to identifyone or more criteria for locally processing at least a portion of speechinput on-device.
 12. The system of claim 11, wherein the contentmetadata associated with the speech input represents a likelihood thatthe corresponding ASR request will be successfully processed by theserver-side query processing stack.
 13. The system of claim 11, whereinthe content metadata associated with the speech input represents alikelihood that processing of the corresponding ASR request will have animpact on a user associated with the user device.
 14. The system ofclaim 11, wherein the content metadata associated with the speech inputand generated by the user device comprises at least one of: a loginindicator indicating whether or not a user associated with the userdevice is logged in to the user device; a speaker-identification scorefor the speech input indicating a likelihood that the speech inputmatches a speaker profile associated with the user device; or abroadcasted-speech score for the speech input indicating a likelihoodthat the speech input corresponds to broadcasted or synthesized speechoutput from a non-human source.
 15. The system of claim 11, wherein thecontent metadata associated with the speech input and generated by theuser device comprises at least one of: a hotword confidence scoreindicating a likelihood that one or more terms preceding the voice queryin the speech input corresponds to a predefined hotword; an activityindicator indicating whether or not a multi-turn-interaction is inprogress between the user device and the query processing backend; anaudio signal score of the speech input; or a spatial-localization scoreindicating a distance and position of a user relative to the userdevice.
 16. The system of claim 11, wherein the content metadataassociated with the speech input and generated by the user devicecomprises at least one of: a transcription of the speech input generatedby an on-device ASR module residing on the user device; a user devicebehavior signal indicating a current behavior of the user device; or anenvironmental condition signal indicating current environmentalconditions relative to the user device.
 17. The system of claim 11,wherein determining whether the server-side query processing stack isoverloaded is based on at least one of: historical data associated withprevious ASR requests communicated by the user device to the server-sidequery processing stack; a schedule of past and/or predicted overloadconditions at the server-side query processing stack; or receiving anoverload condition status notification from the server-side queryprocessing stack on the fly indicating a present overload condition atthe server-side query processing stack.
 18. The system of claim 11,wherein executing the on-device processing instructions furthercomprises: transcribing, by the data processing hardware, the speechinput using a local ASR module residing on the user device; interpretingthe transcription of the speech input to determine a voice querycorresponding to the speech input; determining whether the user devicecan execute an action associated with the voice query corresponding tothe speech input; and executing the action associated with the voicequery when the user device is able to execute the action.
 19. The systemof claim 11, wherein executing the on-device processing instructions toidentify the one or more criteria comprises executing the on-deviceprocessing instructions to identify one or more thresholds thatcorresponding portions of the content metadata must satisfy in order forthe user device to transmit the ASR request to the server-side queryprocessing stack.
 20. The system of claim 19, wherein the operationsfurther comprise dropping ASR request when at least one of thethresholds are dissatisfied.